The present invention relates to thermal management of microelectronic packaging and dice, and, more particularly, to active cooling using electrokinetic fluid pumping and internal cooling microchannels.
A microelectronic package comprises a microelectronic die electrically interconnected with a carrier substrate, and one or more other components, such as electrical interconnects, an integrated heat spreader, a heat sink, among others. An example of a microelectronic package is an integrated circuit microprocessor. A microelectronic die comprises a plurality of interconnected microcircuits within a carrier to perform electronic circuit functions.
A microelectronic die generates heat as a result of the electrical activity of the microcircuits. In order to minimize the damaging effects of heat, passive and active thermal management devices are used. Such thermal management devices include heat sinks, heat spreaders, and fans, among many others. There are limitations in the use of each type of device, and in many cases, the thermal management device is specifically designed for a particular microelectronic die and package design and intended operation.
Heat sinks are one type of passive thermal management device. The heat sink provides the transfer of heat from the surface of the microelectronic die to a large thermal mass, which itself incorporates a large surface area to convectively transfer the heat to the surrounding environment. Effective heat sinks tend to be very large and have sophisticated design with regards to fins and or pin heat releasing appendages.
Integrated heat spreaders (IHS) are passive thermal conducting lids or caps placed in intimate thermal contact with the backside surface of the microelectronic die. Integrated heat spreaders also have sides that extend to seal against the carrier substrate, containing and protecting the microelectronic die and the electrical interconnects from the environment. An integrated heat spreader also provides an enlarged flat surface into which a heat sink may be attached.
Non-uniform power distribution across the microelectronic die results in local areas of high heat flux (hot spots) that must be mitigated. The thermal management device must be able to maintain these hot spots at or below a specified temperature. This is very difficult when the local heat can be 10-times the microelectronic die average. Current devices are overwhelmed and limited in their ability to mitigate these local high heat flux sources. The thermal resistance between the heat sink and/or heat spreader is not low enough to adequately provide the necessary thermal mitigation in a reasonably sized system.
Currently, the localized heat generation is dissipated away from the microelectronic die once the heat has diffused to the surface. An IHS, heat sink, and/or a fan coupled to the surface does not have a major effect on spreading heat at the local-level within the microelectronic die. As a result, high temperature gradients and high-localized temperatures will continue to exist using the external methods of cooling.
Apparatus and methods are needed to mitigate the effects of non-uniform power distribution and for providing means of removing of dissipating the the required heat flux distribution across the microelectronic die. They must provide for exceptionally small-scale integration, not interfere with the electrical interface of other components within the microelectronic package, and be inexpensive to manufacture.